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Calc polygon area from KML

#kml   #python   #geo   #gis  

Table of Content

Calc polygon area from KML#

KML#

Keyhole Markup Language (KML) is an XML notation for expressing geographic annotation and visualization within two-dimensional maps and three-dimensional Earth browsers (wikipedia)

KML tags can divide into three categories 1. Feature 2. Geometry 3. Style

Feature#

Container Tag for our Demo, Placemark hole Geometry and metadata for specific location

Geometry#

  • Point
  • LineString
  • Polygon
  • Linear Ring

Style#

Drawing style for different geometries

Code#

The demo KML contain one placemark with one polygon

Packages#

fastkml#

pygeoif#

pyproj#

shaply#

"""
pip install fastkml
pip install shapely
pip install pyproj
"""
from fastkml import kml
from fastkml.kml import Placemark, Document
from pygeoif.geometry import Polygon
from pyproj import Geod
import shapely.geometry.polygon
from os import path

file_path = "/workspaces/gis_tutorial/data/test.kml"
with open(file_path, "r", encoding="utf-8") as f:
    doc = f.read()
k = kml.KML()
# lxml support encoding issue
doc = bytes(bytearray(doc, encoding="utf-8"))
k.from_string(doc)
features = list(k.features())

document: Document = features[0]
placemark: Placemark
for placemark in document.features():
    geo: Polygon = placemark.geometry
    poly_points = [(lat, lon) for lat, lon, _ in geo.exterior.coords]
poly_points.reverse()
poly = shapely.geometry.polygon.Polygon(poly_points)
geod = Geod(ellps="WGS84")
poly_area, poly_perimeter = geod.geometry_area_perimeter(poly)

print(poly_area)
print(poly_perimeter)

Reference#